Page 410 - Geosystems An Introduction to Physical Geography 4th Canadian Edition

374 part III The Earth–Atmosphere Interface
50°
50°
40°
Meiji Seamount
160° 30°
Alaska
NORTH AMERICA
Hawaii
1000 MILES 1000 KILOMETERS
Suiko Seamount (59.6)
Nintoku Seamount (56.2)
40°
Ojin Seamount
Kimmei Seamount
Jingu Seamount (55.4)
Koko Seamount (48.1) Yuryaku Seamount
Abbott Seamount
Hawaiian-Emperor bend
20°
180°
0 0
Hawaii
Daikakuji Seamount
0
20°
30°
Direction of Pacific plate
movement
Kure
Midway (27.7)
Pearl and Hermes
Reef
Northampton Bank
(38.7)
Laysan (20.0)
= Exposed island
250 500 KILOMETRES
Gardner Pinnacles
Necker (10.3) Nihoa
Ni‘ihau
Moloka‘i Läna‘i
The islands and seamounts
in the chain are progressively younger toward the southeast.
Maui (1.3) Hawai‘i (0.4)
La Perouse Pinnacle
Kaua‘i (5.1) O‘ahu (2.6)
170° 180°
Hot-spot location
170° 160°
Lö‘ihi (newest forming future island)
(a)
▲Figure 12.22 Hot-spot tracks across the North Pacific. Hawai‘i and the linear volcanic chain of islands known as the Emperor Seamounts. (a) The islands and seamounts in the chain are progressively younger toward the southeast. Ages, in m.y.a., are shown in parentheses. note that Midway Island is 27.7 million years old, meaning that the site was over the plume 27.7 m.y.a. [(a) After D. A. Clague, “Petrology and K–Ar (Potassium–Argon) ages of dredged volcanic rocks from the western Hawaiian ridge and the southern Emperor seamount chain,” Geological Society of America Bulletin 86 (1975): 991; inset map courtesy of nOAA.]
Animation
Hot-Spot Volcano Tracks
islands and seamounts with ages increasing northwest- ward away from the hot spot. The oldest island in the Hawaiian part of the chain is Kaua‘i, approximately 5 million years old; today, it is weathered and eroded into the deep canyons and valleys pictured on the cover of this book.
To the northwest of Hawai‘i, the island of Midway rises as a part of the same system. From there, the Em- peror seamounts spread northwestward and are progres- sively older until they reach about 40 million years in age. At that point, this linear island chain shifts direc- tion northward. This bend in the chain is now thought to be from both movement in the plume and a possible change in the plate motion itself, a revision of past
thinking that all hot-spot plumes remain fixed relative to the migrating plate. At the northernmost extreme, the seamounts that formed about 80 m.y.a. are now ap- proaching the Aleutian Trench, where they eventually will be subducted beneath the Eurasian plate.
The big island of Hawai‘i, the youngest in the island chain, actually took less than 1 million years to build to its present stature. The island is a huge mound of lava, formed from magma from several seafloor fissures and volcanoes and rising from the seafloor 5800 m to the ocean surface. From sea level, its highest peak, Mauna Kea, reaches an elevation of 4205 m. This total height of almost 10000 m represents the highest mountain on Earth if measured from the ocean floor.
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Emperor Seamounts
Emperor Seamounts
Hawaiian Ridge